Hey! In this house, we obey the Laws of Thermodynamics!

Well Maybe AP2K will break the laws of physics and build a perpetual motion machine.

...but hey laws were made to be broken right?

So has anybody done a real efficiency comparison of a mechanical compressor to an all-electric thermo-electric cooler? (AKA Peltier junction)
I know they're pretty expensive but I suspect they are probably a lot more efficient.

quote Originally posted by jscott1: Are you really an Electrical Engineer?

I'm just a spectator here, but I was beginning to wonder the same thing myself.


Edit --- Noted 9 April 2008 in another thread:

quote Originally posted by AP2k: ... (Junior EE major. )

[This message has been edited by Marvin McInnis (edited 04-10-2008).]

quote Originally posted by jsantini: So has anybody done a real efficiency comparison of a mechanical compressor to an all-electric thermo-electric cooler? (AKA Peltier junction) I know they're pretty expensive but I suspect they are probably a lot more efficient.

Peltiers aren't efficient. They're an expensive way to cool a CPU, let alone an automobile interior.

Here is an electric car that I would buy...

Notice with all the technology it's still just only slightly more efficient than an all gas car, and it achieves that efficiency at the expense of using stored engery from being plugged in for 8 hours.

If it didn't have a plug and only relied on energy generated by the gas engine, it would be less efficient than if you hooked the gas engine up directly to the wheels.

http://www.chevrolet.com/in...tvoltdevelopment.jsp

I was in Home Depot looking at the generators and noticed something curious...

The 13KW generator had a 30 hp gasoline engine.

30 hp = 22,380 watts mechanical energy

turns into

13,000 watts electricity

efficiency of 58%

Almost half your mechanical energy is lost somewhere.

I have a Hybrid Escape. The AC runs off of the engine like other cars. When I go below 40 MPH or stop, so does the AC. On a hot day at a long red light, it can start to get warm. However, the AC controls have Orange positions for AC and defrost. When you turn the dial to an Orange position, the engine keeps running. (And cooling)

I think this Chevy Volt is a cool idea but it is what we need to convince people that are addicted to the oil companies that electric is a good way to go. Everyone gets hung-up on the range. They're not realizing that 40 miles will take 90% of us where we want to go every day! I believe this is a step towards pure electric cars. People will see that their engine hardly ever runs and wonder why we can't just put more batteries in and remove the gas engine.
The Phoenix Motorcar pure electric SUT goes 100+ miles per charge, at about $3.00 for the electric. I can make electricty on my roof, (Solar), or in my yard, (Wind). I can't make gasoline at my house.

quote Originally posted by GT40 Kit 3.8 SC: I can make electricty on my roof, (Solar), or in my yard, (Wind).

Yes, but can you make enough electricity in 24 hours to make that 40 mile trip in your electric car? Do the numbers and get back to us.

Solar and wind power are good ideas, but as jscott1 has already noted, the power density of sunlight and wind is really low.

It's true the power densities of solar and wind are very very low. I preach that all the time, it's not the cost or efficiency of solar panels that make them impractical.

However, that doesn't mean we shouldn't be developing solar and wind energy for usage.

Except for nuclear power...all energy on the Earth originally came from the sun, to grow plants, which fed dinosaurs, which evenually turned into oil, and refined into gasoilne...to the more direct wind and hydro...it's all solar.

The trick is to collect it and concentrate it in a usable form. You wouldn't want an array the size of a football field in your yard to recharge your electric car, but there are plenty of wide open spaces in West Texas they could build arrays and send the power to where it's needed. The lines losses are relatively low such that it's feasible.

If everyone had an electric car in their garage, I promise you the motivation would be there to develop renewable forms of electricity.

quote Originally posted by jscott1: ... that doesn't mean we shouldn't be developing solar and wind energy for usage.

I agree completely! My key point is that there isn't a single "silver bullet" energy technology (direct solar, wind, geothermal, biomass, tidal, hydrogen, nuclear, etc.) out there that's going to solve all of our energy problems.

Example: The average electrical power consumption in my (rather large but efficient) home last year was substantially less than 5 kw. The peak load, however, was at least ten times that, and the house is wired for a maximum demand of 96 kw. I would be delighted if I could cost-effectively generate 4 kw on site for the base load through some combination of solar and wind, and then depend upon the utility grid to supply the demand peaks. Unfortunately, though, our peak demand occurs during the summer air conditioning season, when everybody else's demand peaks too.

quote Originally posted by Marvin McInnis: The peak load, however, was at least ten times that, and the house is wired for a maximum demand of 96 kw.

You and I are completely on the same page! Unless Cold Fusion, zero point energy or some other exotic breakthrough energy appears, we will have to solve the energy crunch on many fronts.

As I said earlier, the International Space Station with those 4 gigantic arrays, in pure unfiltered sunlight only make 75 KW, barely enough to power a normal house. Can you imagine having an array twice that size, (to account for clouds) and a room full of batteries, (for night). It's not going to work that way.

I'm counting on Mr. Fusion. Just toss you organic trash into the hopper and voila! Free electricity!!

Actually they already have that. It's big, noisy, and generates some farily toxic black glass as a by-product. But it will even turn nuclear waste into energy. There was an article in Popular Science (and I'm sure many other places) about it. They can park one next to a garbage dump and turn all the crap into energy. (and toxic glass) But at least it's a solid form instead of a greenhouse gas that floats up to the atmosphere.
(Edit - found it on PopSci. Found another guy who's also invented one. Google "Gasification plant".)
http://www.popsci.com/popsc...04eecbccdrcrd/2.html

[This message has been edited by Riceburner98 (edited 08-23-2007).]

quote Originally posted by jscott1: It's true the power densities of solar and wind are very very low. I preach that all the time, it's not the cost or efficiency of solar panels that make them impractical.

The 600 W/m2 number you quoted earlier is low. That's what you get when you put a solar panel on the ground at that latitude. If you use the panel intelligently and orient it perpendicular to the solar flux, you get about 1000 W/m2. Latitude doesn't matter.

there is a lot of energy that our curent solar cells are not useing there is other waves of light that we cant convert yet

quote Originally posted by chrisgtp: ... there is other waves of light that we cant convert yet

???

quote Originally posted by jscott1: I was in Home Depot looking at the generators and noticed something curious... The 13KW generator had a 30 hp gasoline engine. 30 hp = 22,380 watts mechanical energy turns into 13,000 watts electricity efficiency of 58% Almost half your mechanical energy is lost somewhere.

I'm not a physicist, or an Electrical Engineer, but my guess would be
Heat. (thermal radiation)

[This message has been edited by IFLYR22 (edited 08-24-2007).]

quote Originally posted by Will: The 600 W/m2 number you quoted earlier is low. That's what you get when you put a solar panel on the ground at that latitude. If you use the panel intelligently and orient it perpendicular to the solar flux, you get about 1000 W/m2. Latitude doesn't matter.

You need to know latitude to know what angle to put the solar panel at. Latitudes closer to the equator have a greater energy density because the sun's energy doesn't have to go through as much atmosphere to reach the solar panel. Closer to the polls, the energy is coming in at more of an angle, so it goes through more atmosphere before reaching the solar panel.

Fusion will be our savior ultimately.
It's also not just about the gas we burn in our cars. Its the oil we use for our plastics, our rubber, our paints, our medicines, roads buildings glass everything. Everything uses oil.

quote Originally posted by Will: The 600 W/m2 number you quoted earlier is low. That's what you get when you put a solar panel on the ground at that latitude. If you use the panel intelligently and orient it perpendicular to the solar flux, you get about 1000 W/m2. Latitude doesn't matter.

The 600 W/m2 is an average based on latitude and Clouds.

Latitude DOES matter, you can't just orient the panel perpendicular to the flux and make up for the fact that the rays have traveled through more atmosphere and are spread out over a larger area, than an area on the Earth where the surface is perpendicular to the flux. The difference is the whole reason why we have seasons. In the northern hemisphere, in Dec, Jan, and Feb we are actually closer to the Sun than in June, July and Aug, and the flux in Earth Orbit is higher, but the angle of incidence creates winter nonetheless.

Also as you get futher away from the equator your hours of daylight are going to decrease during the winter necessitating more batteries to make up for it.

[This message has been edited by jscott1 (edited 08-25-2007).]

quote Originally posted by jscott1: I was in Home Depot looking at the generators and noticed something curious... The 13KW generator had a 30 hp gasoline engine. 30 hp = 22,380 watts mechanical energy turns into 13,000 watts electricity efficiency of 58% Almost half your mechanical energy is lost somewhere.

well i'm only a dumbed down construction worker. but here's my opinion on this. i think that people generally go by bigger is better. my generator at the house is a raider arc 10kw. it's only powered by a 20hp v twin honda. don't feel like doing any math, but i would guess that mine's a little better on the numbers.

quote Originally posted by Billybo455: well i'm only a dumbed down construction worker. but here's my opinion on this. i think that people generally go by bigger is better. my generator at the house is a raider arc 10kw. it's only powered by a 20hp v twin honda. don't feel like doing any math, but i would guess that mine's a little better on the numbers.

True, it could be that the 30 hp engine is not operating at peak capacity for the rated 13 KW, to prolong engine life.

20 HP = 15 kW (14.913 kW, actually)

So if you get 10 kW out for 15 kW in, that's 67% efficiency. That's still in the same ballpark. Likely the 30 HP engine is oversized either for durability, or because people like to see bigger numbers on their generators.

FYI, Google is great for doing conversions for you. I typed in "20 hp to watts" and it gave me the answer in Watts.

Google's calculator is quite handy.

i was on my way to work when i was typing it. i just wanted to get my point out there. :P

quote Originally posted by Billybo455: well i'm only a dumbed down construction worker ....

Don't sell yourself short. It's not necessarily about education and what you do for a living, it's more about knowledge and your way of thinking. Never confuse credentials with competence.

quote Originally posted by jscott1: The 600 W/m2 is an average based on latitude and Clouds. Latitude DOES matter, you can't just orient the panel perpendicular to the flux and make up for the fact that the rays have traveled through more atmosphere and are spread out over a larger area, than an area on the Earth where the surface is perpendicular to the flux.

Why not? For every photon that misses the panel due to diffraction through the air, there's one more from an adjacent ray of light that hits the panel when it wouldn't have without the atmospheric effect. If the effect is enough to consider, why don't you quantify it?
And if that number is an average for latitude and clouds, then you should have said so when you posted that number.
Now if you're talking about atmospheric absorbtion, you might have a case, but again, you need to quantify that effect.

quote Originally posted by chrisgtp: there is a lot of energy that our curent solar cells are not useing there is other waves of light that we cant convert yet

quote Originally posted by Marvin McInnis: ???

Although some advancement has been made recently, current "off the shelf" solar cell tech takes very little advantage of light energy in the UV portion of the spectrum.

[This message has been edited by dguy (edited 08-29-2007).]